1. Field of the Invention
This invention relates to a decorative laminated sheet possessing high surface hardness and excelling in gloss, flexibility, light resistance, stain resistance, water resistance, chemical resistance, and crack resistance and to a decorative overlaid plywood excelling in surface hardness, gloss, light resistance, stain resistance, water resistance, chemical resistance, and crack resistance.
2. Description of the Prior Art
Among the decorative laminated sheets and decorative overlaid plywoods heretofore known to the art are counted such thermoplastic resin decorative laminated sheets and decorative overlaid plywoods which are obtained by coloring or printing patterns on polyvinyl chloride resin films or polyester films and pasting these films on plywoods and hardboards. The thermosetting resin decorative laminated sheets produced by the method which comprises impregnating colored or pattern-printed sheets of paper or cloth severally with melamine resin, benzoguanamine resin, phenol resin, unsaturated polyester resin, etc. or with copolycondensation products of such resins and, at the same time, curing the impregnated sheets and the thermosetting resin decorative overlaid plywoods produced by the method which comprises preparing the same impregnated sheets of paper or cloth and curing these sheets integrally with substrates are also counted among the conventional decorative laminated sheets and decorative overlaid plywoods mentioned above. Of these decorative laminated sheets and decorative overlaid plywoods, the thermoplastic resin decorative laminated sheets and decorative overlaid plywoods possess highly desirable flexibility and enjoy rich freedom of fabrication but are deficient in surface hardness, heat resistance, and chemical resistance. The thermosetting decorative laminated sheets and decorative overlaid plywoods possess high surface hardness and excel in heat resistance and chemical resistance. They nevertheless are deficient in flexibility and are liable to sustain cracks or fractures during the course of transportation or fabrication. They also have the disadvantage that they tend to sustain cracks owing to changes in such environmental conditions as temperature and humidity and they exhibit poor light resistance.
The decorative laminated sheets and decorative overlaid plywoods using melamine resin, for example, enjoy improvement in gloss, water resistance, and chemical resistance when they are cured under the conditions used during the course of forming. They nevertheless have the disadvantage that the crack resistance is degraded as the curing proceeds further. None of the decorative laminated sheets and decorative overlaid plywoods known to the art fulfils all the physical properties.
The copolycondensate of cyclohexanecarboguanamine or norbornanecarboguanamine with melamine, to be used in the present invention and the use of this copolycondensate as a material for molding are dislcosed in U.S. Pat. No. 3,379,661. It has been known that the shaped articles obtained from this molding material are excellent in light resistance and stain resistance. The U.S. Patent discloses nothing about the use of the copolycondensate in decorative laminated sheets or decorative overlaid plywoods. Because the method is used for forming the copolycondensate as the molding material to produce a shaped article, it does not follow that this method ought to be applicable to the production of decorative laminated sheets and decorative overlaid plywoods using the same copolycondensate. Further, it has been difficult to conceive out of the prior art a method for the production of the aforementioned copolycondensate in form fit for the production of decorative laminated sheets or decorative overlaid plywoods. The U.S. Patent makes absolutely no mentioned of the copolycondensate's flexibility and crack resistance. It has been difficult, therefore, to find out of the prior publication the possibility of the copolycondensate yielding the various properties which decorative laminated sheets and decorative overlaid plywoods are expected to possess.
An object of this invention, therefore, is to provide novel decorative laminated sheets and decorative overlaid plywoods.
Another object of this invention is to provide a decorative laminated sheet which possess high surface hardness and excels in flexibility, gloss, light resistance, stain resistance, water resistance, chemical resistance, and crack resistance and a decorative overlaid plywood having a resin-impregnated sheet layer integrated with a substrate and excelling in surface hardness, gloss, light resistance, stain resistance, water resistance, chemical resistance and crack resistance.